Fnhon Ultegra Di2 12 Speed: Geometry Comparison with Aethos

With the Fnhon Ultegra Di2 12 speed folding bike completed, I will now compare it with the Specialized Aethos. Reason for this comparison is to show the differences in geometry between an standard full-sized road bike and a folding bike with drop bars.

Before comparing bike geometry, align the bottom bracket, as this is the datum for all other bike measurements.

Both the saddles are adjusted to my height, but the Fnhon saddle is taller, as the bottom bracket is higher from the ground.

The bottom bracket of the Fnhon is about 300 mm from the ground, while the Aethos is only 260 mm. Therefore, if the distance between the bottom bracket and saddle is the same across different bikes, the saddle height from the ground will be higher, when the bottom bracket is higher.

The Aethos has a slightly longer chainstay of 410 mm, compared to 400 on the Fnhon. Hard to see the difference visually.

Fnhon has a longer front centre distance compared to the Aethos.

There is a huge difference in handlebar height here! The Dura-Ace and Ultegra Di2 shifters have the same functionality, just with different appearance.

The handlebar on the Fnhon is about 70 mm higher. Accounting for the 40 mm bottom bracket height difference, the effective handlebar height difference (relative to the saddle) is 30 mm higher on the Fnhon.

Other than the height difference, the reach of the handlebar from the saddle is quite similar. On the Fnhon, the Controltech Stem can be rotated forward or backwards to adjust the reach.

The rider will be higher up on the Fnhon bike, by about 40 mm, which is the bottom bracket height and also saddle height difference.

Different wheel size and handlebar height.

Other than the higher handlebar position, the riding geometry has been adjusted to be similar to the optimum position, as measured during the bike fitting.

This is the final part of the 3-way bike swap! The Dahon MuSP and Birdy have been completed earlier.

I have sold away the Dahon MuSP, which leaves me with the Birdy and Fnhon folding bikes.

These two folding bikes are quite different, which is what I wanted, to avoid too much duplication of function and usage.

Birdy AXS 12 speed has a smaller 406 wheel size, but with full suspension and flat handlebar setup. It uses a full SRAM AXS 12 speed drivetrain, with XTR brakes. This bike folds down rather compactly and fits at the back of a car. Built for comfortable casual rides, using premium components.

Fnhon Ultegra Di2 12 speed has a larger 451 wheel size, with drop bars for fast road riding. Not as fast as a road bike, but still fast compared to most folding bikes. Uses a full Ultegra Di2 12 speed drivetrain for best braking and shifting performance. Handlebar sticks out quite a lot when folded, so it is less compact. Still fits in the back seat of a car, but not the rear boot.

Both folding bikes weigh about 9.2 kg without pedals and kickstand (add about 500 grams for pedals and kickstand). Both use full hydraulic disc brakes for best braking performance, and also electronic shifting for effortless shifting.